This group is related to sedatives. Where as the term sedative describes drugs that serve to calm or relieve anxiety, the term hypnotic generally describes drugs whose main purpose is to initiate, sustain, or lengthen sleep. Because these two functions frequently overlap, and because drugs in this class generally produce dose-dependent effects (ranging from anxiolysis to loss of consciousness) they are often referred to collectively as sedative-hypnotic drugs.[2]

Hypnotic drugs are regularly prescribed for insomnia and other sleep disorders, with over 95% of insomnia patients being prescribed hypnotics in some countries.[3] Many hypnotic drugs are habit-forming and, due to a large number of factors known to disturb the human sleep pattern, a physician may instead recommend changes in the environment before and during sleep, better sleep hygiene, the avoidance of caffeine or other stimulating substances, or behavioral interventions such as Cognitive Behavioral Therapy for Insomnia (CBT-I) before prescribing medication for sleep. When prescribed, hypnotic medication should be used for the shortest period of time necessary.[4]

Among individuals with sleep disorders, 13.7% are taking or prescribed nonbenzodiazepines, while 10.8% are taking benzodiazepines, as of 2010.[5] Early classes of drugs, such as barbiturates, have fallen out of use in most practices but are still prescribed for some patients. In children, prescribing hypnotics is not yet acceptable unless used to treat night terrors or somnambulism.[6] Elderly people are more sensitive to potential side effects of daytime fatigue and cognitive impairments, and a meta-analysis found that the risks generally outweigh any marginal benefits of hypnotics in the elderly.[7] A review of the literature regarding benzodiazepine hypnotics and Z-drugs concluded that these drugs can have adverse effects, such as dependence and accidents, and that optimal treatment uses the lowest effective dose for the shortest therapeutic time period, with gradual discontinuation in order to improve health without worsening of sleep.[8]

Falling outside the above-mentioned categories, the neuro-hormone melatonin has a hypnotic function.[9]

Research about using medications to treat insomnia evolved throughout the last half of the 20th century. Treatment for insomnia in psychiatry dates back to 1869 when chloral hydrate was first used as a soporific.[11]Barbiturates emerged as the first class of drugs that emerged in the early 1900s,[12] after which chemical substitution allowed derivative compounds. Although the best drug family at the time (less toxic and with fewer side effects) they were dangerous in overdose and tended to cause physical and psychological dependence.[13][14][15]

Benzodiazepines are not without their drawbacks; substance dependence is possible, and deaths from overdoses sometimes occur, especially in combination with alcohol and/or other depressants. Questions have been raised as to whether they disturb sleep architecture.[16]

Nonbenzodiazepines are the most recent development (1990s–present). Although it's clear that they are less toxic than their predecessors, barbiturates, comparative efficacy over benzodiazepines have not been established. Without longitudinal studies, it is hard to determine; however some psychiatrists recommend these drugs, citing research suggesting they are equally potent with less potential for abuse.[17]

Other sleep remedies that may be considered "sedative-hypnotics" exist; psychiatrists will sometimes prescribe medicines off-label if they have sedating effects. Examples of these include mirtazapine (an antidepressant), clonidine (generally prescribed to regulate blood pressure), quetiapine (an antipsychotic), and the over-the-counter sleep aid diphenhydramine (Benadryl – an antihistamine). Off-label sleep remedies are particularly useful when first-line treatment is unsuccessful or deemed unsafe (for example, in patients with a history of substance abuse).

Benzodiazepines can be useful for short-term treatment of insomnia. Their use beyond 2 to 4 weeks is not recommended due to the risk of dependence. It is preferred that benzodiazepines be taken intermittently and at the lowest effective dose. They improve sleep-related problems by shortening the time spent in bed before falling asleep, prolonging the sleep time, and, in general, reducing wakefulness.[20][21] Like alcohol, benzodiazepines are commonly used to treat insomnia in the short-term (both prescribed and self-medicated), but worsen sleep in the long-term. While benzodiazepines can put people to sleep (i.e., inhibit NREM stage 1 and 2 sleep), while asleep, the drugs disrupt sleep architecture: decreasing sleep time, delaying time to REM sleep, and decreasing deep slow-wave sleep (the most restorative part of sleep for both energy and mood).[22][23][24]

Other drawbacks of hypnotics, including benzodiazepines, are possible tolerance to their effects, rebound insomnia, and reduced slow-wave sleep and a withdrawal period typified by rebound insomnia and a prolonged period of anxiety and agitation.[25][26] The list of benzodiazepines approved for the treatment of insomnia is fairly similar among most countries, but which benzodiazepines are officially designated as first-line hypnotics prescribed for the treatment of insomnia can vary distinctly between countries.[21] Longer-acting benzodiazepines such as nitrazepam and diazepam have residual effects that may persist into the next day and are, in general, not recommended.[20]

It is not clear as to whether the new nonbenzodiazepine hypnotics (Z-drugs) are better than the short-acting benzodiazepines. The efficacy of these two groups of medications is similar.[20][26] According to the US Agency for Healthcare Research and Quality, indirect comparison indicates that side-effects from benzodiazepines may be about twice as frequent as from nonbenzodiazepines.[26] Some experts suggest using nonbenzodiazepines preferentially as a first-line long-term treatment of insomnia.[21] However, the UK National Institute for Health and Clinical Excellence (NICE) did not find any convincing evidence in favor of Z-drugs. A NICE review pointed out that short-acting Z-drugs were inappropriately compared in clinical trials with long-acting benzodiazepines. There have been no trials comparing short-acting Z-drugs with appropriate doses of short-acting benzodiazepines. Based on this, NICE recommended choosing the hypnotic based on cost and the patient's preference.[20]

Older adults should not use benzodiazepines to treat insomnia unless other treatments have failed to be effective.[27] When benzodiazepines are used, patients, their caretakers, and their physician should discuss the increased risk of harms, including evidence which shows twice the incidence of traffic collisions among driving patients as well as falls and hip fracture for all older patients.[3][27]

Nonbenzodiazepines are a class of psychoactive drugs that are very "benzodiazepine-like" in nature. Nonbenzodiazepine pharmacodynamics are almost entirely the same as benzodiazepine drugs and therefore entail similar benefits, side-effects, and risks. Nonbenzodiazepines, however, have dissimilar or entirely different chemical structures, and therefore are unrelated to benzodiazepines on a molecular level.[17][29]

Research on nonbenzodiazepines is new and conflicting. A review by a team of researchers suggests the use of these drugs for people that have trouble falling asleep but not staying asleep,[note 2] as next-day impairments were minimal.[30] The team noted that the safety of these drugs had been established, but called for more research into their long-term effectiveness in treating insomnia. Other evidence suggests that tolerance to nonbenzodiazepines may be slower to develop than with benzodiazepines.[not in citation given] A different team was more skeptical, finding little benefit over benzodiazepines.[31]

In common use, the term antihistamine refers only to compounds that inhibit action at the H1 receptor (and not H2, etc.).

Clinically, H1 antagonists are used to treat certain allergies. Sedation is a common side-effect, and some H1 antagonists, such as diphenhydramine (Benadryl) and doxylamine, are also used to treat insomnia.

^When used in anesthesia to produce and maintain unconsciousness, "sleep" is metaphorical as there are no regular sleep stages or cyclical natural states; patients rarely recover from anesthesia feeling refreshed and with renewed energy.

^Because the drugs have a shorter elimination half life they are metabolized more quickly: nonbenzodiazepines zaleplon and zolpidem have a half life of 1 and 2 hours (respectively); for comparison the benzodiazepine clonazepam has a half life of about 30 hours. This makes the drug suitable for sleep-onset difficulty, but the team noted sustained sleep efficacy was not clear.

^Benca, R. M. (March 2005). "Diagnosis and treatment of chronic insomnia: a review". Psychiatr Serv. 56 (3): 332–43. doi:10.1176/appi.ps.56.3.332. PMID15746509. Evidence for the utility of currently available nonbenzodiazepine hypnotics points to their primary efficacy as sleep-onset, rather than as sleep-maintenance, agents. Once again, longer-term randomized, double-blind, controlled studies that demonstrate efficacy of these agents have not been performed, but safety over the longer term has been demonstrated in open-label studies, with minimal evidence of rebound phenomena. By comparison with benzodiazepines, there has been less evidence of subjective and objective next-day residual effects associated with zolpidem or subjective next-day impairment with zaleplon, even when the latter has been delivered in the middle of the night.